A. Field of the Invention
The present invention relates to a novel arrangement and method for the emergency rescue and unloading of an incapacitated ready mix truck.
B. Description of the Prior Art
It is well known in the art to supply concrete to a construction site using a ready mix truck. The drum, which contains and mixes the water and other ingredients into the cement or concrete, typically spins at 12-14 rpm to thoroughly mix the components together. The drum is operated (rotated) by a hydraulic motor connected to a gearbox connected to the base of the drum. The hydraulic motor is powered by a hydraulic pump driven by a drive shaft connected to the front of the truck engine. When power from the motor is interrupted because of engine failure or a myriad of other reasons, the drum quits rotating. If the drum is stationary, then the concrete will start to set (“harden”) in the drum. After a period of time, which can be as short as one half hour to 3 hours depending on the particular mix and other variables, the concrete will set in the drum potentially ruining the drum.
After the concrete has hardened in the drum, it is common procedure to remove and replace the drum at considerable cost, including the crane required to lift the drum off the truck and place the new one on the truck. The operator may also suffer a period of down time waiting for a new drum to be delivered. As an option, a jack hammer operator can be inserted into the drum to jack hammer the concrete out of the drum. This may be a considerably lengthy and costly process depending on the amount of concrete in the drum. The manager faced with the decision to try and save the drum by using a jack hammer operator may also be faced with strict OSHA, EPA and other agency requirements for ensuring the safety and well being of the jack hammer operator while working inside the drum thereby increasing the cost of the repair.
There have been several attempts to maintain the drum in motion or to restart the drum after power from the motor is interrupted. One such device is shown in U.S. Pat. No. 4,097,925 to Butler, Jr. The patent shows a hydraulic emergency power unit mounted on a trailer which can be driven to the truck and linked to the hydraulic system of the truck to rotate a drum of a failed mixer truck to unload the concrete. However this system requires an extensive trailer system and may not be agile enough to reach construction locations where the ready mix trucks typically frequent. It may also be logistically difficult to secure a second truck with a hitch to pull the trailer or to find an operator to drive the truck. As well, it may be difficult to maneuver the trailer into a position close enough to link the hydraulic hoses of the trailer mounted pump to the hydraulic motor of the ready mix drum.
The current invention proposes an arrangement for a portable emergency drum jumper which can be mounted to the mixer fender or mixer fender of a truck to provide emergency power to rotate the drum. The pump has been substantially reduced in size by rotating the drum at reduced speed sufficient to mix in a retarder or water that will prevent the concrete for setting up to 24 hours to provide time to unload the concrete from the drum. Instead of attempting to duplicate the power and drum rotation rate of 12-14 rpm of a fully operational truck, the emergency drum jumper operates at a slower rate such as 2 rpm which is sufficient to mix the retarder or water fully into the concrete and to allow unloading of the concrete. While the higher speed of the fully operational truck allows for expedited on-site mixing of the concrete for a particular job, the lower speed of the emergency hydraulic pump of the current invention provides a fully capable portable system which can be easily delivered on site.